Çocuk portakal suyunu pipetle içiyor ve çok mutlu görünüyor.

Because portakal suyu means orange juice, and in this sentence it is the specific thing the child is drinking.

• su = water
• portakal suyu = orange juice

When a definite/direct object is used in Turkish, it usually takes the accusative ending.
So:

• portakal suyu = orange juice
• portakal suyunu = the orange juice / orange juice (as the specific object being drunk)

Why -nu?

• The base form here is suyu
• Then the accusative ending is added
• Because of Turkish sound rules, it becomes suyu + n(u) = suyunu

That extra n is a buffer consonant often used when a suffix is added after a third-person possessive form.

This is just how Turkish expresses juice in many common phrases.

• portakal = orange
• su = water
• portakal suyu = orange juice

Turkish often forms compounds this way. A few similar examples:

• elma suyu = apple juice
• üzüm suyu = grape juice
• limon suyu = lemon juice / lemon juice or lemon liquid depending on context

So even though it literally looks like orange water, the meaning is simply orange juice.

Pipetle means with a straw or using a straw.

It comes from:

• pipet = straw
• -le / -la = with, by means of

So:

• pipetle içiyor = he/she is drinking with a straw

This ending is very common for tools or means:

• kaşıkla = with a spoon
• bıçakla = with a knife
• elle = by hand / with the hand

İçiyor is the present continuous form, which is very commonly used in Turkish for actions happening right now.

• içmek = to drink
• içiyor = is drinking / drinks (in the current situation)

In this sentence, the child is actively doing the action, so içiyor fits naturally.

By contrast:

• içer often means drinks in a more habitual or general sense, like He drinks orange juice

So:

• Çocuk portakal suyunu içiyor = The child is drinking the orange juice
• Çocuk portakal suyu içer = The child drinks orange juice / drinks orange juice in general

Turkish often leaves out subject pronouns when they are already clear from context or from the verb.

Here, çocuk means child, so the subject is already stated. There is no need to add o.

• Çocuk ... içiyor = The child is drinking ...
• O ... içiyor = He/She is drinking ...

Since çocuk is already the subject, adding o would usually be unnecessary unless you want extra emphasis.

This is an important vocabulary point.
The verb görünmek means to appear, to look, to seem, not to see.

• görmek = to see
• görünmek = to appear / to look / to seem

So:

• çok mutlu görünüyor = he/she looks very happy

Even though it resembles görmek, it is a different verb with a different meaning.

In Turkish, adjectives can often be used directly before verbs like görünmek to describe how someone appears.

• mutlu = happy
• çok mutlu görünüyor = looks very happy

This is a very natural structure:

• yorgun görünüyor = looks tired
• hasta görünüyor = looks sick
• üzgün görünüyor = looks sad

Mutludur would mean something more like he/she is happy, often with a slightly more formal, factual, or emphatic tone. But here the sentence is about appearance, so görünüyor is the right choice.

Because çok means very here, and in Turkish it comes before the adjective it modifies.

• çok mutlu = very happy

This is the normal order in Turkish:

• çok güzel = very beautiful
• çok iyi = very good
• çok küçük = very small

So çok mutlu görünüyor literally follows the pattern very happy looks.

Ve simply means and.

It connects the two actions/descriptions:

• Çocuk portakal suyunu pipetle içiyor
• ve çok mutlu görünüyor

So the full sentence says that the child is both:

1. drinking orange juice with a straw, and
2. looking very happy

This works much like English and.

The sentence is:

Çocuk portakal suyunu pipetle içiyor ve çok mutlu görünüyor.

A rough breakdown is:

• Çocuk = subject
• portakal suyunu = object
• pipetle = instrument/manner
• içiyor = verb
• ve = and
• çok mutlu = description
• görünüyor = verb

Turkish often prefers Subject + Object + Verb, unlike English, which usually uses Subject + Verb + Object.

So:

• English: The child is drinking orange juice
• Turkish: The child orange juice is drinking

Also, Turkish often places details like with a straw before the verb.

Yes, Turkish word order is somewhat flexible, but different orders can sound more marked or emphasize different parts.

The neutral version here is:

• Çocuk portakal suyunu pipetle içiyor.

You could also hear:

• Çocuk pipetle portakal suyunu içiyor.

This still means basically the same thing. The difference is mostly about emphasis or style.

However, the verb usually stays near the end in standard Turkish sentences, especially in neutral statements.

Because çocuk is the subject of the sentence, and Turkish subjects in a simple statement are often just in the basic dictionary form.

• çocuk = child

No special ending is needed here.

Compare:

• Çocuk içiyor. = The child is drinking.
• Çocuğu görüyorum. = I see the child.

In the second sentence, çocuk becomes çocuğu because it is now the object, not the subject.

Çocuk means child in general. It does not by itself tell you whether the child is male or female.

So in English, depending on context, it could be translated as:

• the child
• the kid
• sometimes the boy if the context or picture clearly shows a boy

But grammatically, the Turkish word itself is gender-neutral.

Turkish does not have articles exactly like English a/an and the.

Instead, definiteness is often shown in other ways, especially through context and case marking.

In this sentence:

• çocuk can mean the child because the context makes it identifiable
• portakal suyunu shows a definite object because of the accusative ending

So Turkish often expresses what English does with the by using structure rather than a separate word.

Because there is no plural marker on it.

• su = water
• suyu = his/her/its water or the compound form in portakal suyu
• suyunu = that specific water/juice as object in this structure

If it were plural, you would usually see -lar / -ler somewhere:

• sular = waters
• portakal sularını = the orange juices (as object), depending on context

Here, suyunu is singular.

It comes from görünmek = to appear / to look / to seem.

The form görünüyor can be understood as:

• verb stem: görün-
• present continuous marker: -iyor
• third person singular: no extra ending is needed

So:

• görünüyor = he/she/it is appearing / looks / seems

In natural English, çok mutlu görünüyor is best translated as looks very happy rather than the more literal is appearing very happy.